Electron channeling X-ray microanalysis for site occupation in β-FeSi2 doped with Co

The site occupation state of Co atoms in a thermoelectric semiconductor Fe0.97Co0.03Si2 of the β-FeSi2 structure was analyzed by measuring and calculating characteristic X-ray intensities at various electron incidence directions in a transmission electron microscope (TEM). The analysis technique used was recently developed from the method for determining atomic locations by channeling-enhanced microanalysis (ALCHEMI). The calculation was based on dynamical electron diffraction and inelastic scattering theories, and the calculated intensities were compared with the measured intensities. The intensities depended on the occupation site of Co atoms and sample thickness. As a result, the occupation probabilities of Co atoms on Fe I and II sites, which were difficult to be determined by the conventional ALCHEMI technique, were shown to be 0.0333 and 0.0257, respectively.